In the past, a chemical absorption method (using, for example, amine absorbent (for example, an absorbent, such as N-methyl diethanolamine: MDEA)) and a physical absorption method (using a Selexol absorbent that uses, for example, polyethylene glycol dimethyl ethers) have been proposed as a technique that removes acid gases, such as CO2 and H2S, contained in a gasified gas obtained through the gasification of coal or biomass performed by a gasification furnace.
Incidentally, there are following demands in the case of a system such as an IGCC (integrated coal gasification combined cycle) technique.
1) In a power generation system, it is necessary to remove H2S, which is a generation source of SOX, in order to make the discharge of SOX, which is an air pollutant, be lower than a criterion. On the other hand, it is preferable that CO2 is not recovered as much as possible in order to obtain an effect of improving power generation efficiency.
2) Since a case where a recovered gas (off-gas) containing H2S has a lower flow rate and higher H2S concentration is advantageous when a chemical product is manufactured from the recovered gas or when H2S is processed, it is preferable that H2S can be selectively recovered.
3) In a system where CO shift and CCS (recovery/storage of carbon dioxide) are combined with IGCC, it is necessary to suppress H2S concentration of CO2, which is recovered in a CO2 recovery process, to about a criterion (for example, 10 to 20 ppm).
4) In order to improve power generation efficiency, it is preferable that the amount of heat energy such as steam to be used be small.
That is, it has been required that H2S is separated from a gas, which contains CO2 and H2S, efficiently and selectively in terms of heat energy.
Accordingly, an energy saving process for supplying a part of an absorbent, where soluble ingredients are partially diffused in a bursting container (an upper stage of a regenerator), to the lower side from the top of an absorber has been proposed in the past (Patent Literature 1).